Question

Figure shows a man pulling a rope with such a force that the plank is held in position. The weights of the ropes, plank and pulleys are to be neglected. If $g=10m{s}^{-2}$ and the weight of the man is $80kgf$, then the force with which the man pulls the rope is

• A. 100 N
• B. 200 N
• C. 400 N
• D. 800 N

Answer 1

Answer: (B)

$T$ is tension due to ropes and $N$ is the normal force between mass and plank. The force with which man pulls down the rope is the Tension $T$ of the ro For equilibrium of man,
$T+N=mg$
$\Rightarrow T+3T=mg$
$T=\frac{mg}{4}=\frac{80\times 10}{4}=200N$